30 CHEMISTRY, AS APPLIED TO THE 



absorbed by water, and does not precipitate lime-water. It is inflammable, 

 burning with a beautiful blue flame ; the product of its combustion is Carbonic 

 Acid. This gas differs strikingly from the former in its properties, though we 

 have already seen that it only differs in constitution by containing a little more 

 oxygen, carbonic oxide being C 2 O (two volumes of C to one of O), and car- 

 bonic acid C O (equal volumes of the same elements) . It is pungent and aci- 

 dulous, soluble in water, to which it communicates the briskness we admire in 

 soda-water. It is considerably heavier than common air, T524 being its spe- 

 cific gravity. It renders lime-water turbid, causing a precipitate of carbonate 

 of lime. It is perfectly incombustible, and extinguishes burning bodies when 

 immersed in it. It is produced by many natural operations, such as the fer- 

 mentation of vegetable juices : it is formed wherever carbon is burned with a 

 full supply of oxygen, and is also formed during the earlier stages of the de- 

 composition of coal ; but when a considerable body of coke has been formed 

 in the retort, any carbonic acid which may have been produced unites with a 

 portion of this coke in passing over it, and forms the previously-described 

 compound, C 2 O. Carbon unites with hydrogen in many proportions, and 

 many of these compounds are produced during the distillation of coal, but the 

 only two of importance are carburetted hydrogen and olefiant gas. 



CARBURETTED HYDROGEN is abundantly formed in nature in stagnant pools, 

 ditches, etc., wherever vegetables are undergoing the process of putrefaction : 

 it also forms the greater part of the gas obtained from coal. Carburetted 

 hydrogen consists of 100 volumes of vapour of carbon and 200 of hydrogen ; 

 these during combination are condensed into one volume : we may repre- 

 sent it by H 2 C. It is colourless, and almost inodorous ; is not dissolved to 

 any extent by water ; and is much lighter than atmospheric air, its density 

 being 0'5594. It is very inflammable, burning with a strong yellow flame : the 

 products of its combustion are carbonic acid and water. Mixed with chlorine, 

 no action takes place when quite dry ; but if moist (that is, containing the 

 vapour of water) and exposed to sunshine, it is decomposed by this element. 

 The fire-damp of coal-mines consists almost exclusively of carburetted hydro- 

 gen gas. 



OLEFIANT GAS is thus named from having the property of uniting and form- 

 ing an oily substance with chlorine. It is a product of the distillation of oil, 



